> ## Documentation Index > Fetch the complete documentation index at: https://kb.spektrumglasses.com/llms.txt > Use this file to discover all available pages before exploring further. # Why do some blue light lenses reflect blue? > Some blue light lenses show a blue-purple sheen because they filter light with a multi-layer coating that reflects a slice of the blue-violet band (roughly # Why do some blue light lenses reflect blue? **By [Spektrum Glasses Editorial Team](https://kb.spektrumglasses.com/how-we-choose)** · Published 2026-08-14 · Updated 2026-09-11 · Facts re-checked 2026-09-11 *How this page is written and checked: [our editorial method](https://kb.spektrumglasses.com/how-we-choose) · [how we verify claims](https://kb.spektrumglasses.com/how-we-verify)* ## Short answer Some blue light lenses show a blue-purple sheen because they filter light with a multi-layer coating that reflects a slice of the blue-violet band (roughly 400-450 nm) off the lens surface instead of absorbing it. The sheen is a side effect of how that coating works, not a measurement of how much blue light the lens actually filters. * Coated clear lenses reflect part of the 400-450 nm band, which produces the visible blue-purple sheen. * Dye-based tinted lenses (yellow, orange, red) absorb blue light instead of reflecting it, so they look colored rather than shiny. * A visible sheen is not a filtration percentage; only spectrophotometer testing measures that. * ANSI Z80.3 tests light transmittance and color, not the accuracy of a reading power. * Evidence that filtered blue light changes eye strain or sleep outcomes is limited and contested. ## What causes the sheen Clear blue-light lenses are usually filtered with a thin-film interference coating: several microscopically thin layers deposited on the lens surface that are tuned to reflect a narrow slice of wavelengths rather than let them pass through. When that reflected slice falls in the blue-violet part of the spectrum, the lens throws back a blue or purple flash under overhead light or on camera. It looks like a special effect, but it is the coating doing its job - light that isn't transmitted through the lens has to go somewhere, and a reflective coating sends it back out toward the viewer instead of absorbing it as heat. Our own clear lens (COLTS Laboratories report O-SPG111015) shows why the sheen concentrates where it does: it filters 99.99% at 400 nm and 95.1% at 410 nm, but that falls to 63.0% at 420 nm and 33.1% at 450 nm. The coating is doing most of its work at the short-wavelength, near-violet edge of the visible spectrum and tapering off by the time it reaches 450 nm - which is consistent with a reflective sheen that reads as blue-violet rather than an even, colorless dimming across the whole band. ## Coating versus tint: two different mechanisms Not every blue-light lens filters the same way. A coated clear lens reflects a narrow band and otherwise passes the rest of the visible spectrum through close to unchanged - our clear lens transmits 91.6% of visible light overall (photopic transmission), which is why it reads as nearly clear rather than tinted. A dye-based lens, like our yellow evening lens from the same COLTS report, instead absorbs a wider slice of the spectrum with pigment mixed into or coated onto the lens: it filters 98% of the 400-500 nm blue band, 99.9% of high-energy visible (HEV) light, and 98.3% at the 460-480 nm band associated with melatonin research, at the cost of dropping visible transmission to about 65%. | Lens | Band filtered | Visible transmission | Mechanism | | ---------------- | --------------------------------------------- | -------------------- | ------------------ | | Clear | 99.99% at 400 nm, tapering to 33.1% at 450 nm | 91.6% | Reflective coating | | Yellow (evening) | 98% of 400-500 nm | about 65% | Absorptive dye | Because the yellow lens absorbs rather than reflects, it produces far less of a visible sheen off the surface - instead it changes the color of everything seen through it, which is the trade a wearer is actually making with a heavier tint. ## A sheen is not a filtration measurement It is tempting to judge a lens by how strongly it flashes blue in a photo, but the intensity of that reflection is not a reliable stand-in for the percentage of blue light actually filtered. Reflection strength depends on coating design, viewing angle, and light source, none of which map cleanly onto a transmittance percentage. The only way to know what a lens filters is to measure it on a spectrophotometer across defined wavelength bands, the way our clear and yellow lenses were measured in COLTS Laboratories report O-SPG111015, run under ISO/IEC 17025 accreditation (A2LA certificate 1612.01) to the ANSI Z80.3 spectral transmittance and chromaticity method. That report's clear lens samples passed ANSI Z80.3 transmittance and chromaticity testing as a category 0 cosmetic lens. It is worth being precise about what that standard covers: Z80.3 governs how much light gets through a lens and what color it is, not whether a stated reading power is accurate. A lens can pass Z80.3 and say nothing about its magnification - the two are tested, and should be described, separately. ## Clear lenses are not all the same "Clear blue-light lens" is a description of appearance, not a filtration spec, and two lenses that both look clear can filter very differently. Our coated clear lens filters 99.99% at 400 nm down to 33.1% at 450 nm. By comparison, a ZENOX clear lens measured about 52% average across the blue band while still blocking 100% of UV. A shopper looking at either lens on a shelf cannot tell them apart by eye, and cannot use the presence or absence of a reflective sheen to rank them - only the published band-by-band transmittance numbers can do that. ## What filtering the light changes, and what is still unresolved Reducing the amount of blue-violet light that reaches the eye is a measurable optical outcome: a 2017 PLOS ONE study (Leung, Li & Kee) found that commercially available blue-light-filtering lenses reduced the calculated blue-light hazard - the modeled proportion of blue light reaching the eye - by roughly 10 to 24 percent compared with unfiltered lenses. What that optical reduction translates to for the wearer is a separate, less settled question. A November 2025 Frontiers in Neurology meta-analysis of three randomized controlled crossover trials (n=49, measured with actigraphy) found no significant difference in sleep onset timing, total sleep time, sleep efficiency, or nighttime waking between blue-blocking and standard lenses, concluding that current trial evidence does not support meaningful effects on those measures. A January 2026 paper in Therapeutic Advances in Ophthalmology (Khorrami-Nejad et al.) similarly found minimal or no significant difference in contrast sensitivity, color discrimination, or task performance versus standard lenses, and describes the picture for symptom-level outcomes as still debated. The published, measured transmittance data is solid; claims about how that translates into daily comfort or sleep are not yet backed by consistent evidence. ## The trade-off at the tinted end Push filtration further and the trade-off becomes more visible. Our orange and red lenses, measured in 2026 by our lens manufacturer's optical laboratory, filter 99.96% and 99.83% respectively across the 380-500 nm band - far more of the band than either the clear or yellow lens - but they do it with heavy dye absorption that noticeably shifts perceived color. Neither is suitable for driving. That is the underlying trade running through all of these lens types: a near-clear coated lens keeps color perception close to normal by reflecting a narrow slice of the spectrum, while a deeply tinted absorptive lens filters much more of the band at the cost of how colors look through it. A blue-purple sheen sits at the mild end of that spectrum - a byproduct of a coating doing a small, targeted job, not a shortcut for judging how much light any given lens actually filters. ## Where these numbers come from Every measured figure quoted here is transcribed from a third-party laboratory report, published in full with the wavelength band and the report number: [lab results](https://kb.spektrumglasses.com/lab-results). Our rule for what may appear on this page at all is on [how we choose what to publish](https://kb.spektrumglasses.com/how-we-choose). ## Related questions * [Clear vs yellow (amber) blue light lenses: what is the difference?](/answers/clear-vs-amber-blue-light-lenses) * [What do orange lenses do?](/answers/what-do-orange-lenses-do) * [What do red lenses do?](/answers/what-do-red-lenses-do) * [Do clear blue light lenses actually work?](/answers/do-clear-blue-light-lenses-work) * [What percentage of blue light should glasses block?](/answers/what-percentage-blue-light-should-be-blocked) * [Why do some blue light glasses have a yellow tint?](/answers/yellow-tint-explained) ## A PROSPEK style for this Ships from Amazon (Prime, 30-day returns). Sold by PROSPEK by Spektrum Glasses.